In 3GPP RAN LTE (3rd Generation Partnership Project Radio Access Network Long Term Evolution), single carrier transmission of low PAPR (Peak to Average Power Ratio) has been studied as one of uplink transmission schemes.
In single carrier transmission schemes, as a method of improving frequency diversity effect, DFT-spread-OFDM (Discrete Fourier Transform-spread-Orthogonal Frequency Division Multiplex) scheme is disclosed in Patent Document 1. As shown in FIG. 1, in DFT-spread-OFDM, symbol data is subjected to FFT (Fast Fourier Transform) processing, and “0” is inserted into output data from the FFT processing section, so that the frequency band for use is expanded. That is, the frequency band for transmission becomes wider, and, consequently, frequency diversity effect is improved.
FIG. 2 shows the transmission spectrum and level variations in frequency selective channels in single carrier transmission disclosed in Patent Document 1. In a radio channel, the transmission spectrum shown in FIG. 2 is influenced by frequency selective fading as shown in the figure. That is, specific frequency components in the received signal are deteriorated. In the receiving side, waveform distortion due to frequency selective fading is reduced by frequency domain equalization techniques, for example.
Patent Document 1: Japanese Patent Application Laid-Open No. 2005-117581